The periodic table model of the gender transpositions: Part I. A theory based on masculinization and defeminization of the brain

Students of human sexuality have long tried to make sense of atypical masculinity, femininity, sexual object choice, gender identity, or clothing choice. In Part I of this paper, we propose a theory to organize and to make sensible most of the major facts about these gender transpositions—a periodic table model of the gender transpositions. People have neural substrates that have been subjected to particular combinations of two distinct biobehavioral processes: masculinization and defeminization. In our theory, we hypothesize that individuals exhibit behaviors reflecting particular degrees of masculinization and/or defeminization, at least probabilistically. Therefore, each sexological group is characterized by a distinct distribution of its members centered about one particular combination of the two. Many other facts about the gender transpositions, as well as about aspects of gender roles in typical men and women, then flow from the theory. We also consider the possible mechanisms of brain masculinization and defeminization—noting genetic, hormonal, and environmental influences.